unrecoverable exception on G5 with CONFIG_PPC_EARLY_DEBUG enabled
Denis Kirjanov
kda at linux-powerpc.org
Fri Jun 17 05:49:08 AEST 2016
>> Ok, the issue was introduced by the commit
>> caca285e5ab4a7a19fede51688106ceed6fc45dd (powerpc/mm/radix: Use
>> STD_MMU_64 to properly isolate hash related code) and 970mp dies on
>> the following condition:
>
>> +BEGIN_MMU_FTR_SECTION
>> bl slb_allocate_realmode
>> -
>> +END_MMU_FTR_SECTION_IFCLR(MMU_FTR_RADIX)
>
> Thanks.
>
> How did you work that out?
>
> That FTR section says to call slb_allocate_realmode() when MMU_FTR_RADIX is
> clear (ie. zero). That should always be the case on your machine, unless
> you've
> plugged a Power9 into your G5 ;)
>
>> In my config I've enabled radix MMU lookup but in my understanding
>> only recent IBM machines support this feature and we have to call SLB
>> entry through slb_allocate_realmode on HPTE machine?
>
> That's right, and that's what the code should be doing.
>
> My G5 is booting OK:
>
> michael at cogito:~$ uname -a
> Linux cogito 4.7.0-rc3-gdb06d75 #1 SMP Thu Jun 16 05:16:31 AEST 2016 ppc64
> GNU/Linux
>
> michael at cogito:~$ cat /proc/cpuinfo
> processor : 0
> cpu : PPC970FX, altivec supported
> clock : 1599.999000MHz
> revision : 3.0 (pvr 003c 0300)
>
> timebase : 33333333
> platform : PowerMac
> model : PowerMac8,1
> machine : PowerMac8,1
> motherboard : PowerMac8,1 MacRISC4 Power Macintosh
> detected as : 338 (iMac G5)
> pmac flags : 00000000
> L2 cache : 512K unified
> pmac-generation : NewWorld
>
> michael at cogito:~$ zgrep RADIX /proc/config.gz
> CONFIG_PPC_RADIX_MMU=y
>
> michael at cogito:~$ dmesg|grep _features
> [ 0.000000] cpu_features = 0x0804806318100448
> [ 0.000000] cpu_user_features = 0xdc080000 0x00000000
> [ 0.000000] mmu_features = 0x0c000001
> [ 0.000000] firmware_features = 0x0000000000000000
>
> In particular notice:
>
> #define MMU_FTR_RADIX ASM_CONST(0x80000000)
> mmu_features = 0x0c000001
>
> ie. MMU_FTR_RADIX is clear.
>
> Do you see a different value for mmu_features?
Oops, I messed things up, sorry :/
The reason is here:
/* All done -- return from exception. */
ld r10,PACA_EXSLB+EX_LR(r13)
@@ -1384,7 +1399,9 @@ slb_miss_realmode:
lwz r9,PACA_EXSLB+EX_CCR(r13) /* get saved CR */
mtlr r10
-
+BEGIN_MMU_FTR_SECTION
+ b 2f
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_RADIX)
andi. r10,r12,MSR_RI /* check for unrecoverable exception */
beq- 2f
So with the patch we got the direct jump to label 2 :
c000000000006edc <slb_miss_realmode>:
c000000000006edc: 7d 48 02 a6 mflr r10
c000000000006ee0: 91 2d 01 8c stw r9,396(r13)
c000000000006ee4: f9 4d 01 98 std r10,408(r13)
c000000000006ee8: 48 03 28 09 bl c0000000000396f0
<.slb_allocate_realmode>
c000000000006eec: e9 4d 01 98 ld r10,408(r13)
c000000000006ef0: e8 6d 01 90 ld r3,400(r13)
c000000000006ef4: 81 2d 01 8c lwz r9,396(r13)
c000000000006ef8: 7d 48 03 a6 mtlr r10
c000000000006efc: 48 00 00 38 b c000000000006f34
<slb_miss_realmode+0x58>
c000000000006f00: 71 8a 00 02 andi. r10,r12,2
c000000000006f04: 41 82 00 30 beq c000000000006f34
<slb_miss_realmode+0x58>
c000000000006f08: 7d 38 01 20 mtocrf 128,r9
c000000000006f0c: 7d 30 11 20 mtocrf 1,r9
c000000000006f10: e9 2d 01 a8 ld r9,424(r13)
c000000000006f14: 7d 20 e3 a6 mtppr r9
c000000000006f18: e9 2d 01 50 ld r9,336(r13)
c000000000006f1c: e9 4d 01 58 ld r10,344(r13)
c000000000006f20: e9 6d 01 60 ld r11,352(r13)
c000000000006f24: e9 8d 01 68 ld r12,360(r13)
c000000000006f28: e9 ad 01 70 ld r13,368(r13)
c000000000006f2c: 4c 00 00 24 rfid
c000000000006f30: 48 00 00 00 b c000000000006f30
<slb_miss_realmode+0x54>
c000000000006f34: 7d 7a 02 a6 mfsrr0 r11
c000000000006f38: e9 4d 00 18 ld r10,24(r13)
c000000000006f3c: 61 4a 6f 54 ori r10,r10,28500
c000000000006f40: 7d 5a 03 a6 mtsrr0 r10
c000000000006f44: e9 4d 00 20 ld r10,32(r13)
c000000000006f48: 7d 5b 03 a6 mtsrr1 r10
c000000000006f4c: 4c 00 00 24 rfid
c000000000006f50: 48 00 00 00 b c000000000006f50
<slb_miss_realmode+0x74>
Without the ftr conditional section everything looks fine:
c000000000006edc <slb_miss_realmode>:
c000000000006edc: 7d 48 02 a6 mflr r10
c000000000006ee0: 91 2d 01 8c stw r9,396(r13)
c000000000006ee4: f9 4d 01 98 std r10,408(r13)
c000000000006ee8: 48 03 28 09 bl c0000000000396f0
<.slb_allocate_realmode>
c000000000006eec: e9 4d 01 98 ld r10,408(r13)
c000000000006ef0: e8 6d 01 90 ld r3,400(r13)
c000000000006ef4: 81 2d 01 8c lwz r9,396(r13)
c000000000006ef8: 7d 48 03 a6 mtlr r10
c000000000006efc: 71 8a 00 02 andi. r10,r12,2
c000000000006f00: 41 82 00 30 beq c000000000006f30
<slb_miss_realmode+0x54>
c000000000006f04: 7d 38 01 20 mtocrf 128,r9
c000000000006f08: 7d 30 11 20 mtocrf 1,r9
c000000000006f0c: e9 2d 01 a8 ld r9,424(r13)
c000000000006f10: 7d 20 e3 a6 mtppr r9
c000000000006f14: e9 2d 01 50 ld r9,336(r13)
c000000000006f18: e9 4d 01 58 ld r10,344(r13)
c000000000006f1c: e9 6d 01 60 ld r11,352(r13)
c000000000006f20: e9 8d 01 68 ld r12,360(r13)
c000000000006f24: e9 ad 01 70 ld r13,368(r13)
c000000000006f28: 4c 00 00 24 rfid
c000000000006f2c: 48 00 00 00 b c000000000006f2c
<slb_miss_realmode+0x50>
c000000000006f30: 7d 7a 02 a6 mfsrr0 r11
c000000000006f34: e9 4d 00 18 ld r10,24(r13)
c000000000006f38: 61 4a 6f 50 ori r10,r10,28496
c000000000006f3c: 7d 5a 03 a6 mtsrr0 r10
c000000000006f40: e9 4d 00 20 ld r10,32(r13)
c000000000006f44: 7d 5b 03 a6 mtsrr1 r10
c000000000006f48: 4c 00 00 24 rfid
c000000000006f4c: 48 00 00 00 b c000000000006f4c
<slb_miss_realmode+0x70>
>
> cheers
>
>
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